I have a group of layers. I want to apply a hue saturation such that when I make a change to it, it affects all of the layers in the group and sub groups.
While on this topic, is it also possible to apply blending effects such as bevel and emboss to a group of layers?
You can do two things:
Put Adjustment layer above your group (with subgroups of course), convert the group to Smart object and create Clipping mask for your Adjustment layer with your newly created Smart object.
Put Adjustment layer above your group but select both, an Adjustment layer and a group and convert them to Smart object together.
I would, personally, use the first solution because that way you can change your Adjustment layer settings without opening the Smart object.
As for your second question, Bevel and emboss isn't a blending effect but the Layer effect. And yes, you can apply it to a group but not in the way you probably think. It won't add the effect to each object inside group separately but instead apply it as if the group was just one object. If you want that, just convert your group to Smart object and apply the Bevel and emboss effect to that new object. That way your group is still editable. If you don't want your group to be editable, merge group (right click the group and select Merge group) and apply the effect to it instead.
Just create an Adjustment Layer above the groups you want it to affect (it will alter everything below it).
To do this, go to:
LAYER > NEW ADJUSTMENT LAYER > HUE/SATURATION and click OK
Now whenever you want to make changes, just double-click on the new adjustment layer you created. You can twiddle with all the settings to your heart's content, and not have to worry about it permanently altering anything.
rlesko did a good job of answering the second part of your question. (Short answer: "Not really".)
Now the adjustment layer affects that area only.
